A plurality of consecutively arranged transport rolls are typically employed to transport strip-shaped carrier materials such as steel plates, paper sheets, or films, and each of the transport rolls is driven by a dedicated motor. A motor controller is used to control such motors. A typical conventional motor controller includes a speed controller that receives input of a deviation between a speed command and a motor speed, calculates a speed compensation torque that causes the speed command to match an actual speed based on calculation of a proportional control (P control) or a proportional integral control (PI control) based on the received deviation, and adds the speed compensation torque to a motor torque command.
In the above motor controller, the material to be carried is restrained and transported with the transport rolls. In this process, even if a slight difference constantly occurs between the speed command and the speed of a motor operating in conjunction with the carrier material, the speed controller provides control so that no large torque is constantly generated. To realize this, a droop control has been employed. In the droop control, for example, a speed command is subtracted from an amount of a speed droop obtained by proportionally multiplying the speed compensation torque. Moreover, to accurately follow a speed command during accelerating and decelerating a carrier material, such a control has also been performed in which, based on a speed command, an acceleration and deceleration compensation torque necessary for accelerating and decelerating a motor are calculated, and the acceleration and deceleration compensation torque is added to a motor torque command (for example, see Patent Document 1).
Other control has also been performed in which a feedforward compensation is added to a torque command. This feedforward compensation can be a torque necessary for applying tension to a carrier material, or a torque for compensating for machine loss due to friction or the like (for example, see Non-patent Document 1).
[Patent Document 1] Japanese Patent Application Laid-open No. H4-121086 (FIG. 1)
[Non-Patent Document 1] “Technology for strip tension control in continuous annealing line”, Proceedings of the Japan Industry Applications Society Conference 1991, pp. 800-801